Create 400_Nth_Digit.cc

cpppy · web-flow · commit 4edb308097ba · 2016-09-21T20:33:54.000+08:00
diff --git a/400_Nth_Digit.cc b/400_Nth_Digit.cc
@@ -0,0 +1,24 @@
+class Solution {
+public:
+    int findNthDigit(int n) {
+        int i=1;
+        int sum=0;
+        while(sum<n) {
+            sum += 9*pow(10,i-1)*i;
+            i++;
+        }
+        i--;
+        sum -= 9*pow(10,i-1)*i;
+        int prei=i-1;
+        int prenum=0;
+        while(prei>0){
+            prenum = prenum*10+9;
+            prei--;
+        }
+        int num=prenum+(n-sum+i-1)/i;
+        int y=(n-sum)%i;
+        if(y==0) y=i;
+        int num2=num/pow(10,i-y);
+        return num2%10;
+    }
+};
